De Valk started out as a consultant for companies like:
eBay,
The Guardian,
Disney, and other major companies. Working on the plugin was a
hobby in his spare time. De Valk started a blog in 2004, and by 2005 his website for
SEO was named "joostdevalk.nl". After moving to and eventually selling the domain "css3.info," de Valk created the Yoast platform in 2007. At first, the Yoast company was to consult before he developed both the Yoast SEO plugin and a Google Analytics plugin, both for
WordPress. In 2012, De Valk released a premium version of Yoast SEO. In April 2016, Yoast BV sold the Google Analytics for WordPress plugin. In June 2020, Yoast acquired the Duplicate Post plugin, another very popular WordPress plugin. The software that De Valk created runs on more than nine million websites and on 11.4% of the top million sites in the world. On WordPress, the De Valk SEO software has been downloaded five million times. Michael David, the author of
WordPress Search Engine Optimization (2015), referred to it as "the granddaddy of all SEO plugins". In January 2019 De Valk stepped down as CEO to become Chief Product Officer for Yoast and began working for WordPress in marketing. De Valk left his position with WordPress after six months citing a failure to see his place in the organization. De Valk and his wife are investors in blockchain startup WordProof. In January 2025, in response to the WordPress dispute with
WP Engine, Joost de Valk introduced a blog post announcing his plans for federated and independent repositories to WordPress.org. In response,
Automattic CEO
Matt Mullenweg issued a blog post stating that he will be deactivating the accounts of the contributors, labeling the plans as a "fork" of WordPress, which the contributors denied. ==Personal==